title: Novel surgical classification and treatment strategy for atlantoaxial dislocations.
abstract: METHODS
  Retrospective study of 904 patients with a diagnosis of atlantoaxial dislocation (AAD), using a novel surgical classification and treatment strategy.
  
  
  OBJECTIVE
  To describe a novel surgical classification and treatment strategy for AADs.
  
  
  BACKGROUND
  AADs can result from a variety of etiologies, yet no comprehensive classification has been accepted that guides treatment. Because of the rarity of the cases, however, the treatment strategy has also been debated.
  
  
  METHODS
  During a period of 12 years, a total of 904 patients with a diagnosis of AAD were recruited from a single academic institution. According to the treatment algorithm that included preoperative evaluation using dynamic radiograph, reconstructive computed tomography, and skeletal traction test, the cases were classified into 4 types: I to IV. Types I and II were fused in the reduced position from a posterior approach. Type III, which were irreducible dislocations, were converted to reducible dislocations using a transoral atlantoaxial release, followed by a posterior fusion. Type IV presented with bony dislocations and required transoral osseous decompressions prior to posterior fusion.
  
  
  RESULTS
  Four hundred seventy-two cases were classified as type I, 160 as type II, 268 as type III, and 4 cases as type IV. Follow-up was in the range of 2 to 12 years (average: 60.5 mo). Eight hundred and ninety-nine cases (99.4%) achieved a solid atlantoaxial fusion. Anatomic atlantoaxial reduction was achieved in 892 cases (98.7%), whereas 12 cases had a partial reduction. Neurological improvement was seen in 84.1% (512/609) of the patients with myelopathy. The overall complication rate was 9.1% (82/949).
  
  
  CONCLUSIONS
  Our surgical classification and treatment strategy for AADs was applied in those 904 cases and associated with excellent clinical results with a minimal risk of complications.
  
  
  METHODS
  4.
authors.affiliation: From the Orthopaedic Department, Peking University Third Hospital, Beijing, China.
authors.forename: Shenglin
authors.initials: S
authors.lastname: Wang
authors.forename: Chao
authors.initials: C
authors.lastname: Wang
authors.forename: Ming
authors.initials: M
authors.lastname: Yan
authors.forename: Haitao
authors.initials: H
authors.lastname: Zhou
authors.forename: Gengting
authors.initials: G
authors.lastname: Dang
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001268:Atlanto-Axial Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D002574:Cervical Vertebrae / Q000528:radiation effects / Q000601:surgery; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D004204:Joint Dislocations / Q000145:classification* / Q000175:diagnosis / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D019637:Orthopedic Procedures / Q000295:instrumentation / Q000379:methods*; D017063:Outcome Assessment, Health Care; D015203:Reproducibility of Results; D012189:Retrospective Studies; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods; D014057:Tomography, X-Ray Computed; D014143:Traction / Q000379:methods; D055815:Young Adult